Styryl phosphorodithioate esters to be used as antioxidants in lubricating oil

ABSTRACT

STYRYL ESTER OF O,O-DI(ALKYLPHENYL) PHOSPHORODITHIC ACID ARE PROVIDED AS ANTIWEAR AND ANTIOXIDANT AGENTS FOR HIGH TEMPERATURE SURFACE IN LUBRICATING OILS.

Patented Jan. 26, 1971 sTYavrQPHosPnoRonnmoATE ESTERS TO BE USED AS ANTIOXIDANTS IN LUBRICATING OIL Warren Lowe, El Cerrito, Califl, assignor to Chevron Research Company, San Francisco, Calif., a corporation of Delaware No Drawing. Filed May 31, 1968, Ser. N0. 733,310 Int. Cl. Cm 1/48, 3/42 US. Cl. 25246.6 6 Claims ABSTRACT OF THE DISCLOSURE Styryl esters of 0,0-di(alkylphenyl) phosphorodithioic acid are provided as antiwear and antioxidant agents for high temperature surfaces in lubricating oils.

BACKGROUND OF THE INVENTION Field of the invention In lubricating oils, particularly ash-free or low ash lubricating oils, used in internal combustion engines, it is common to add antioxidant and antiwear agents. Particularly common additives are the zinc salts of various phosphorodithioic acid esters. However, there have been continual efforts to reduce the amount of metal, as their ions, in lubricating oils. The metals during service frequently enhance deposit formation.

Description of the prior art SUMMARY OF THE INVENTION S-wphenylethyl 0,0-di(alkylphenyl) phosphorodithioates, wherein the alkyl group is of from 10 to 18 carbon atoms, having an average of from 12 to 15 carbon atoms, are used in lubricating oils as antioxidants and antiwear agents, particularly for high temperature service in internal combustion engines, e.g., diesel engines.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The phosphorodithioic acid esters which find use in the lubricating oils of this invention have the following formula:

wherein R is alkyl of from 10 to 18 carbon atoms, having an average number of carbon atoms in the range of 12 to 15, preferably a branched chain alkyl, wherein any a branch is of from 1 to 2 carbon atoms, preferably 1 carbon atom (methyl), there being at least 1 branch every 4 carbon atoms along the chain; ,1) is phenyl, and Y is hydrogen or lower alkyl of from 1 to 3 carbon atoms, preferably hydrogen or methyl.

Illustrative groups bonded to sulfur are u-phenylethyl, 2-phenyl-2-propyl, 2-phenyl2-butyl, etc. Illustrative alkyl groups bonded to the phenyl which is bonded to oxygen are polypropenyl, polyisobutenyl, etc.

The phosphorodithioate esters used in this invention are readily prepared by first preparing the 0,0-di-substituted dithiophosphoric acid and reacting the acid at an elevated temperature with the desired olefin. The temperature will generally be in the range of about 50 to 125 C., more usually from to C. The reaction is carried out in the absence of air or other free radical initiator.

The lubricating oils in which the phosphorodithioic acid esters are used may be derived from natural or synthetic sources. Lubricating oils generally have viscosities of from about 35 to 50,000 Saybolt Universal Seconds (SUS) at 100 F.

Among natural hydrocarbonaceous oils are parafiinic base, naphthenic base, asphaltic base and mixed base oils. Illustrative synthetic hydrocarbonaceous oils are polymers of various olefins, generally of from 2 to 8 carbon atoms, and alkylated aromatic hydrocarbons.

The phosphorodithioic acid esters are preferably compounded with from 1 to 15 weight percent of a polyalkylene polyamine lubricating oil detergent. The polyalkylene polyamines will generally have from 2 to 6 nitrogen atoms and alkylene groups of from 2 to 3 atoms. Bonded to the alkylene polyamines will generally be from 1 to 2 oil soluble aliphatic hydrocarbon groups, usually a polymer of olefins of from 3 to 4 carbon atoms (propene and isobutylene). The hydrocarbon groups are bonded to the alkylene polyamine directly to nitrogen or through a nonoxocarbonyl group such as forrnyl or succinoyl. The aliphatic hydrocarbon group Will generally be of from 30 to 200 carbon atoms, more usually of from 50 to carbon atoms.

Illustrative polyalkylene polyamine detergents are found in US. Pats. Nos. 3,219,666, 3,275,554 and 3,087,686.

Other additives may also be present, such as antirust agents, corrosion inhibitors, other detergents, additional oxidation inhibitors, oiliness agents, etc.

The phosphorodithioic acid esters will generally be present in from 1 to 500 mm./ kg. of lubricating oil composition, more usually from about 5 to 50 mm./ kg. Above 100 mm./kg., the composition will be as a concentrate for dilution in use.

The other additives will generally be present individually in from about 0.01 to 15 weight percent, more usually from about 0.05 to 10 weight percent. The alkylene polyamine detergent Will usually be present in from 2 to 15 weight percent.

The following example is offered by way of illustration and not by way of limitation.

Example 0,0-di(alkylphenyl) phosphorodithioic acid (alkyl is polypropenyl of from 12 to 15 carbon atoms) was stirred, after flushing with nitrogen, at 150 F. for 2 hrs. in vacuo, followed by filtering through Celite. Into a 1-liter 3-necked flask equipped with stirrer, heating mantle, thermometer, addition funnel and water condenser was charged 820 g. (0.77 mole) of the acid described above. While stirring the acid at room temperature, 84 g. (0.8 mole) of styrene was slowly added, the temperature rising during the addition but being kept below about 170 F. While maintaining a nitrogen atmosphere, the mixture was stirred at 200 F. for 8 hrs. and then stripped while raising the pot temperature to 250 F. and reducing the pressure to about 2.5 mm. Hg. The residue was filtered through Celite.

Analysis-Percent: P, 2.8; acid No., 2.2 mg. KOH/g.

In order to demonstrate the excellent effectiveness of the phosphorodithioic acid esters utilized in the lubricating oils of this invention, a number of industry-recognized tests were performed.

Compounded oils were prepared and tested in the L-38 Engine Test using a l-cylinder CLR engine. The test is carried out for 40 hrs. with an engine speed of 3,150 r.p.m. The results are reported in bearing weight loss for a copper-lead bearing and also the percent viscosity increase determined at 100 F. as SUS. The following table indicates the results obtained.

TABLE I.L38 ENGINE TEST, 40 HOURS Phcsphoro- Viscosity dithioic 2 Cu-Pb increase Detergent, acid ester, bearing at 100 F., wt. percent n1ni./kg. loss, mg. percent To demonstrate the effectiveness of the lubricating oils under extreme pressure conditions, the oils were tested in the Falex Shear Test. The results are reported as load at failure in pounds.

TABLE II.FALEX SHEAR TEST Load at failure,

Formulation: lbs. Base oil 1 850 Base oil+18 mm./kg. A 2 1,475

480 neutral oil+ wt. percent polyis'obrrtenyl suecinirnide of tctraethylene pentamine (polyisobutenyl -1,000 mol. wt.) and 0.1 Wt. percent terephthalic acid (corrosion inhibitor).

A-s arprhenylethyl 0,0 di(alkylphenyl) phosphorodithioate (alkyl 1s polypropenyl of 12 to 15 carbon atoms).

To demonstrate the effectiveness of the subject additives as antioxidants in lubricating oil compositions, comparison compositions were tested in the Oxidator B Test. In this test, a 25 g. sample is prepared from 480 neutral oil containing the phosphorodithioic acid ester and various other additives normally compounded in a lubricating oil for internal combustion engines. To the 25 g. sample is added 0.2 cc. of a solution having 3,160 p.p.m. of copper, 2,670 p.p.m. of iron, 160 p.p.m. of manganese, 36,700 p.p.m. of lead and 1,630 p.p.m. of tin as their naphthenates. This is considered to be the distribution of metals which would be expected to be found in used crankcase oils after an L-4 Chevrolet Engine Test.

The oil solution to be tested is maintained at 340 F. until 250 ml. of oxygen is absorbed. The results are reported as if a 100 g. sample was used and as the number of hours necessary to absorb 1 liter of oxygen.

4 TABLE III.OXIDATOR B TEST Hrs. to absorb one liter of 0 Base oil +18 mm./kg. of A 2 9.4 Compounded base oil 3 +18 mm./kg. of A 1- 8.7 Base oil -1.0

1 480 Neutral oil. 2 See Table II for definition,

3 480 neutral 0i1+5% of the succinimide described in Table II and 0.1% terephthalic acid.

Finally, the lubricating oil was tested under extreme conditions in a test referred to as the 240 BMEP Caterpillar Engine Test (brake mean effective pressure). The conditions are for a supercharged Caterpillar test, wherein the pressure of the supercharged air is 76.5 in. Hg. abs., the water temperature of the cooling jacket is 200 F.-, the air temperature is F., the oil temperature at the bearing is F., the sulfur content of the fuel is 0.4 Weight percent, the speed of the engine is 1,200 r.p.m., and the rate of fuel input is at a rate which provides 6,900 B.t.u./min. The test was carried out for 60' hrs. using compounded oils. The following table indicates the results:

TABLE IV.240 BMEP CAllfggtgLLAR ENGINE TESIX G O Formulation 1 1 The base oil was a Mid-Continent SAE 30 oil containing 6.25 wt. A, of polyisobutenyl succinimide of tetracthylcnc pentaminc (polyisobutw nyl of 1,000 average moi. weight; the amine is a mixture having the average composition of tetraethyleno pentaininu), and 0.1 weight percent tercphthalio acid.

2 ASee Table II for definition; BZinc-0,0-di(alkylphenyl) phosphorodithioate (alkyl is polypropenyl of 1215 carbon atoms).

3 Groove deposits rated on the basis of 0-100, 100 being completely filled grooves. Land deposits rated on the basis of 0-800, 800 being completely black. Underhead deposits rated on the basis of 0-10, 10 being completely clean.

It is evident from the above results that the styryl ester of the alkylphenyl phosphorodithioate esters provides excellent protection against oxidation of the oil as well as against wear under extremely severe conditions. The ester is frequently as good or superior to the metal salt analogs, yet avoids deposits caused by the presence of metal ions, such as zinc.

As will be evident to those skilled in the art, various modifications of this invention can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the following claims.

I claim:

1. Lubricating oil compositions containing in an effective amount to inhibit oxidation and prevent wear, a composition of the formula:

( JHS wherein R is alkyl of from 10 to 18 carbon atoms, having an average number of carbon atoms in the range of 12 to 15, is phenyl and Y is hydrogen or lower alkyl of from 1 to 3 carbon atoms.

2. A lubricating oil composition according to claim 1, wherein Y is hydrogen and R is branched alkyl.

3. A lubricating oil composition according to claim 2, wherein R is polypropenyl.

4. A lubricating oil composition according to claim 1 having from 2 to 15 weight percent of an alkylene polyamine of from 2 to 6 nitrogen atoms, wherein the alkylene groups are of from 2 to 3 carbon atoms, having bonded to nitrogen from 1 to 2 oil soluble aliphatic hydrocarbon groups of from 30 to 200 carbon atoms, wherein References Cited UNITED STATES PATENTS 2,665,295 1/ 1954 Augustine 260-958 2,589,675 3/1952 Cook et a1 252-466 2,627,523 2/1953 Hook et a1 25246.6

DANIEL E.

6 Hook et a1 252-400 Augustine 252-958 Crosby et a1 252-466 Bacon 260-978 Thompson 252-46.6 LeSuer 252-466 Wagenaar 252-50 WYMAN, Primary Examiner 10 J. M. HICKEY, Assistant Examiner US. Cl. X.R.

Patent No.

UNITED STATES PATENT OFFICE Dated January 26 1971 Inventor(s) (SEAL) Attest:

Attesting Officer EDWARD M.FLETCHER,JR.

Warren Lowe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1 and Column 4 in the formulae Signed and sealed this 15th day of June 1971 WILLIAM E. SCHUYLER, J] Commissioner of Patent:

; FORM PO-105O (IO-69] 

